HSI

Horizontal Situation Indicator

Early HSIs were a vacuum driven compass rose with a lubber line indicator (your heading) and one VOR indicator in the center. The pilot could use the knobs to set the course and use the VOR indicator to see how far off course they were. Rapidly more information was added with the introduction of glass cockpit instruments a moving map was added under the course so the pilot could better see where they were.

Items on the modern HSI

• Compass Rose
• Heading
• Track
• Moving Map
• Map Range
• Course indicator
• Heading indicator (Manually entered or the Autoflyte has selected to target)
• Waypoints
• Navigation fixes (available from the FBO)
• Runways
• Wind Indicator

GPWS map selection and terrain overlay

An active GPWS hazard selects and keeps the MFD on Moving Map in the E-10, E-11, T-19, P-13 and T-27. Clearing the hazard leaves that page selected. Reactive cautions/warnings can select the page without a terrain overlay; routine bank and altitude callouts do not change pages. Hazard inhibit, self-test, ground operation and the in-world simulator do not force a page change. The A-4 and W-6 have separate permanent map displays.

A predictive terrain or obstacle caution/warning automatically selects the terrain overlay; default auto-range selects 10 km inner / 20 km outer range once per encounter. New alerts and escalation appear on the next eligible scan, while brief prediction dropouts retain the highlighted hazard and overlay for up to two seconds. Confirmed clearance restores the normal map presentation and previous range. Read CAUTION TERRAIN versus CAUTION OBSTACLE to distinguish the selected hazard; a yellow patch alone is not necessarily a building. See alert stability for clearance timing, data validity, ground/hover/simulator resets and spaceflight limits.